It's all in the purpose. It has to be asked which brass is best for "what?" If you want precision for benchrest or F class, you may find the high-end brands are best, as mentioned earlier. On the other hand, if you want the most space for powder, you may well be looking at Hornady and Winchester and, if you also need more precision, selecting and prepping them to get the dimensional tolerances you want. If you are shooting a self-loader, you probably want the hardest heads and rims to withstand violent extraction, in which case you will want LC, Starline, or ADG.
You can also get a situation where, as I mentioned earlier, other factors impose your precision limits that aren't curable with brass, like a loose chamber, a mainspring that's getting weak, primer seating practice that is inadequate, poor stock inletting or bedding, a muzzle crown that needs to be redone, etc.
But sometimes not.
One of the authors of the 1994 Precision Shooting Reloading Guide mentioned a 300 Win Mag he just could not get to group below about two moa, no matter what he did with his loading practices until one day, on a lark, he decided to outside turn his case necks. It instantly became a one moa gun. In most guns, you can't see any difference made by outside neck turning, but in that particular gun, it made all the difference, and the author didn't know why. I had an analogous experience with deburring flash holes for 2520 powder. It shot 50% bigger groups than stick powders did in the same rifle (an M1A), but when I deburred the flash holes, it started shooting the smaller groups my stick powders did. I've never seen flash hole deburring have that effect with any other gun or powder.
The bottom line: some things just have to be tried to see if they matter in your particular shooting system. If you have the only gun that cares, no information or advice based on experience with other guns will be apropos. You just have to try it and see.